Journal Article

Occurrence, characterization, and potential predictors of verotoxigenic Escherichia coli, Listeria monocytogenes, and Salmonella in surface water used for produce irrigation in the Lower Mainland of British Columbia, Canada

Pagotto, Franco, Wang, Siyun, Falardeau, Justin, Johnson, Roger P.

2017

Overview

Produce has become a major source of foodborne illness, and may become contaminated through surface water irrigation. The objectives of this study were to (i) determine the frequency of verotoxigenic E. coli (VTEC), Listeria monocytogenes, and Salmonella in surface waters used for irrigation in the Lower Mainland of British Columbia, (ii) assess the suitability of fecal coliforms and generic E. coli as hygiene indicators, and (iii) investigate the correlations of environmental factors with pathogen occurrence. Water samples were collected semi-monthly for 18 months from seven irrigation ditches across the Serpentine and Sumas watersheds. VTEC colonies on water filters were detected using a verotoxin colony immunoblot, and the presence of virulence genes vt1 and vt2 was ascertained via multiplex PCR. Detection of L. monocytogenes and Salmonella was completed using standard, Health Canada Compendium of Analytical Methods. Fecal coliforms and generic E. coli were enumerated by 3M™ Petrifilm™ and filtration methods, and meteorological and geographic data were collected from government records. VTEC, L. monocytogenes, and Salmonella were detected in 4.93%, 10.3%, and 2.69% of 223 samples, respectively. L. monocytogenes occurrence was greatest in the Serpentine watershed (χ2; p < 0.05), and was most common during the winter and fall (Fisher exact test; p < 0.05). Site dependence of VTEC and Salmonella occurrence was observed within watersheds (Fisher's exact test; p < 0.10). Pathogen occurrence correlated with fecal coliform counts (r = 0.448), while VTEC occurrence also correlated with precipitation over the five days before sampling (r = 0.239). The density of upstream livestock correlated with VTEC (rs = 0.812), and L. monocytogenes (rs = 0.841) detection. These data show that foodborne pathogens are present in the waters used for irrigation in the Lower Mainland of British Columbia, but their frequency may depend on spatial and temporal factors.

• Publisher: Public Library of Science,Public Library of Science (PLoS)
• Subject: Agricultural Irrigation / Analytical methods / Bacteria / Biology and Life Sciences / British Columbia / Canada / Coliforms / Colonies / Colony Count, Microbial / Correlation / Disease control / Distribution / Ditches / E coli / Earth Sciences / Environmental aspects / Environmental factors / Epidemics / Escherichia coli / Escherichia coli - isolation & purification / Fecal coliforms / Food contamination & poisoning / Food sources / Foodborne diseases / Foodborne pathogens / Frequency dependence / Health aspects / Health surveillance / Hygiene / Illnesses / Infections / Internet / Irrigation / Irrigation ditches / Irrigation water / Listeria / Listeria monocytogenes / Listeria monocytogenes - isolation & purification / Livestock / Medicine and Health Sciences / Nutrition / Pathogens / Physiological aspects / Precipitation / Public health / Reference services / Research and Analysis Methods / Salmonella / Salmonella - isolation & purification / Surface water / Verotoxin / Virulence / Water analysis / Water filters / Water Microbiology / Water pollution / Water purification / Water quality / Water resources / Water sampling / Watersheds / Winter